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<div class="section" id="compute-ackland-atom-command">
<span id="index-0"></span><h1>compute ackland/atom command</h1>
<div class="section" id="syntax">
<h2>Syntax</h2>
<div class="highlight-default"><div class="highlight"><pre><span></span><span class="n">compute</span> <span class="n">ID</span> <span class="n">group</span><span class="o">-</span><span class="n">ID</span> <span class="n">ackland</span><span class="o">/</span><span class="n">atom</span>
</pre></div>
</div>
<ul class="simple">
<li>ID, group-ID are documented in <a class="reference internal" href="compute.html"><span class="doc">compute</span></a> command</li>
<li>ackland/atom = style name of this compute command</li>
</ul>
</div>
<div class="section" id="examples">
<h2>Examples</h2>
<div class="highlight-default"><div class="highlight"><pre><span></span><span class="n">compute</span> <span class="mi">1</span> <span class="nb">all</span> <span class="n">ackland</span><span class="o">/</span><span class="n">atom</span>
</pre></div>
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</div>
<div class="section" id="description">
<h2>Description</h2>
<p>Defines a computation that calculates the local lattice structure
according to the formulation given in <a class="reference internal" href="#ackland"><span class="std std-ref">(Ackland)</span></a>.</p>
<p>In contrast to the <a class="reference internal" href="compute_centro_atom.html"><span class="doc">centro-symmetry parameter</span></a> this method is stable against
temperature boost, because it is based not on the distance between
particles but the angles. Therefore statistical fluctuations are
averaged out a little more. A comparison with the Common Neighbor
Analysis metric is made in the paper.</p>
<p>The result is a number which is mapped to the following different
lattice structures:</p>
<ul class="simple">
<li>0 = UNKNOWN</li>
<li>1 = BCC</li>
<li>2 = FCC</li>
<li>3 = HCP</li>
<li>4 = ICO</li>
</ul>
<p>The neighbor list needed to compute this quantity is constructed each
time the calculation is performed (i.e. each time a snapshot of atoms
is dumped). Thus it can be inefficient to compute/dump this quantity
too frequently or to have multiple compute/dump commands, each of
which computes this quantity.-</p>
<p><strong>Output info:</strong></p>
<p>This compute calculates a per-atom vector, which can be accessed by
any command that uses per-atom values from a compute as input. See
<a class="reference internal" href="Section_howto.html#howto-15"><span class="std std-ref">Section_howto 15</span></a> for an overview of
LAMMPS output options.</p>
</div>
<div class="section" id="restrictions">
<h2>Restrictions</h2>
<p>This compute is part of the USER-MISC package. It is only enabled if
LAMMPS was built with that package. See the <a class="reference internal" href="Section_start.html#start-3"><span class="std std-ref">Making LAMMPS</span></a> section for more info.</p>
<p>The per-atom vector values will be unitless since they are the
integers defined above.</p>
</div>
<div class="section" id="related-commands">
<h2>Related commands</h2>
<p><a class="reference internal" href="compute_centro_atom.html"><span class="doc">compute centro/atom</span></a></p>
<p><strong>Default:</strong> none</p>
<hr class="docutils" />
<p id="ackland"><strong>(Ackland)</strong> Ackland, Jones, Phys Rev B, 73, 054104 (2006).</p>
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